Centrifugal or forward curved blower wheels may generally comprise a plurality of blades arranged in the form of a cylinder around a solid, central hub disc. During manufacture of a centrifugal blower wheel, a stamping press may be used to form the plurality of blades from a metal sheet. The sheet is gathered between the ends of adjacent blades to reduce the distance between the blades. The sheet, with the material gathered between the blades, is then shaped into a cylinder about the solid, central hub disc. Because the blades are stamped from a single metal sheet, the number of blades and the chords of the blades are limited by the size of the blades and the size of the sheet.
The solid, central hub disc of the centrifugal blower wheel may be formed by stamping a pair of discs from respective rectangular pieces of sheet metal, removing the scrap material for recycling, and joining the discs together. A centrifugal blower wheel may also have one or more end rings deformed onto ends of the plurality of blades to fix the blades in the cylindrical arrangement about the central hub disc. Like the central hub disc, the end rings may be formed by stamping circular rings from rectangular pieces of sheet metal and removing the scrap material for recycling. Stamping the one or more end rings generates additional scrap because each end ring has a central opening formed by removing a circular disc from the center of the end ring. In one approach, the scrap material removed from an end ring to form the central opening can be used as a solid, central hub disc for the centrifugal blower wheel. Although scrap material produced during manufacture of the centrifugal blower wheel may be recycled, the value of the recycled material may not compensate for the costs incurred in cutting, storing, and handling the scrap material.
Mixed flow fans, backward inclined wheels, backward curved wheels, and other centrifugal wheels may have a back disc and an end ring that are both stamped from rectangular pieces of metal, like the central hub disc and end ring(s) of centrifugal blower wheels. Because the back disc and the end ring have a generally circular shape, stamping the circular shapes from rectangular pieces of sheet metal produces scrap in the form of the corner portions of the sheet metal and a circular disc from the center of the end ring. Similarly, traditional approaches for producing a venturi or orifice for a fan assembly or a fan housing include stamping a generally ring-shaped orifice from a rectangular piece of metal. Even if the scrap circular disc from the end ring or orifice is used to produce a back disc, the corner portions of the sheet located outside of the end ring or orifice would still constitute a large amount of scrap material.